1 . In the 1966 science-fiction movie One Million Years B. C., the movie characters had a time travel and arrived in an ancient landscape inhabited by dinosaurs and early humans. The movie was low on science and high on fiction: by then dinosaurs were long dead and modern humans were millions of years away.
A more accurate picture of Earth’s inhabitants at the time is now being revealed. In research published in Nature, a team of scientists led by Anders Gotherstrom at the University of Stockholm, and Love Dalen at the Centre for Palaeogenetics (古遗传学), also in Sweden, describe sequencing (测序) DNA samples from mammoths (猛犸象) that lived and died in north-eastern Siberia around a million years ago.
The team’s work represents a new record, for their mammoth DNA is, by some half a million years, the oldest ever successfully reconstructed. Extracted (提取) from horses, bears and even Neanderthals and Denisovans, two close cousins of modern humans, such ancient DNA has proved an invaluable tool for investigating the past. Although fossils preserve the basic physical features of extinct animals, they are silent about many crucial details that even an incomplete genome (基因组) can help to fill in.
The trouble with DNA is that it breaks down after death. The more broken down it is, the harder it is to sequence. Scientists think that, after about 6m years, all that would be left would be individual base pairs (碱基对), the equivalent of trying to reconstruct a book from several letters. Under the right conditions, however, such as the extreme cold of Arctic permafrost (冻土层) this decay can be slowed.
Dr. Dalen and his colleagues were interested in three mammoth molars (臼齿) extracted in the 1970s from Siberian geological layers that suggested great age. Samples from each were sent to Dr. Dalen’s laboratory in 2017. Having checked they had not been contaminated by bacteria or the shaking hands of Paleontologists, the DNA were extracted, sequenced, and dated. Whereas DNA samples from a living animal can run to several hundreds of thousands of letters, the ancient mammoth samples yielded merely dozens of letter long. This is close to the limit of what is scientifically usable, says a biologist named Ludovic Orlando.
1. What does the underlined word “contaminated” probably mean?A.Protected. | B.Polluted. | C.Estimated. | D.Discovered. |
①the limited number of DNA in mammoth samples
②the break-down of mammoth’s DNA after death
③the wide spread of mammoth samples
④the damage done to the mammoth samples from external environment
⑤the difficulty in extraction of the mammoth’s DNA
A.①②④ | B.②④⑤ | C.②③④ | D.①③④ |
A.The fact that DNA can break down makes it easier to sequence. |
B.The incomplete genome can’t give any details of the extinct animals. |
C.Mammoths’ DNA samples are invaluable for their extremely long history. |
D.The research team created a new record for reconstructing an ancient book. |
A.The movie One Million Years B. C revealed the early human civilization. |
B.Scientists have uncovered the secrets of life by studying mammoths’ DNA. |
C.The mammoths’ DNA may give a clearer picture of ancient inhabitants on earth. |
D.Discoveries of mammoths’ DNA samples help the development of DNA reconstruction technology. |
1.
A.In 1815. | B.In 1848. | C.In 1850. | D.In 1855. |
A.High school education. | B.Two-year study programs. |
C.100 education programs. | D.Four-year college programs. |
A.California has the most state colleges and universities in America. |
B.California is a large city with more than 4, 000, 000 people. |
C.California is the largest state in land area throughout America. |
D.California has only a few high-technology companies. |
3 . As consumers, we are very wasteful. Annually, the world generates 1.3 billion ions of solid waste. This is expected to go up to 2.2 billion by 2025. The developed countries are
Traditional wisdom would seem to suggest that companies have no interest in
When choosing what products to buy and which brands to buy from, more and more consumers are looking into sustainability, which is
Some retailers and manufacturers in the clothing, footwear, and electronics industries have launched
Enormous opportunities also
A.forgivable | B.accountable | C.tolerable | D.remarkable |
A.altering | B.lengthening | C.obeying | D.upsetting |
A.Therefore | B.Somehow | C.Yet | D.Otherwise |
A.partly | B.barely | C.precisely | D.exclusively |
A.bridged with | B.subjected to | C.opposed to | D.associated with |
A.minimizing | B.maintaining | C.stimulating | D.deserting |
A.On the contrary | B.Above all | C.For example | D.In most cases |
A.modifying | B.wrecking | C.dumping | D.restoring |
A.sustainable | B.compulsory | C.economic | D.educational |
A.insuring | B.substituting | C.concealing | D.preserving |
A.accessibility | B.productivity | C.affordability | D.durability |
A.profitable | B.emotional | C.predictable | D.reputational |
A.lie in | B.stand for | C.consist of | D.result in |
A.respectively | B.dramatically | C.evenly | D.thoroughly |
A.take-back. | B.give-away | C.clean-up | D.cut-down |
A.Suitable fertilizers. | B.Adequate water. |
C.Rich soil. | D.Proper temperature. |
Landslide Injures at least 10 in Norwegian Town of Ask
A landslide (山体滑坡) has smashed into a residential area near the Norwegian capital at midnight on Dec. 30. injuring at least 10 people, leaving 21 unaccounted for and
About 700 people have been brought to safety for fear of further landslides.
The landslide cut across a road, leaving a deep gap that cars
Rescue workers continued to search the area for children and adults
Pettersen said there were no reports of missing people, but officials could not rule out the possibility
One of the injured was seriously hurt, while nine had
Norway's King Harald said the landslide had made a deep impression on him. "My thoughts are with all those who are affected, injured or have lost their homes and those who now live in fear and uncertainty of
The area in which Ask
Helicopters continued to circle over the area as night fell
"There could be people trapped ... but at the same time we can't be sure
1.
A.Pink. | B.Green. | C.Purple. | D.White. |
A.Recycling is compulsory. |
B.Most recycling programs don’t succeed in that people don’t want to deliver rubbish. |
C.The primary work of the volunteers is to collect and sort rubbish to the same center. |
D.The volunteers will devote six hours a week to dealing with rubbish. |
A.To explain why recycling is important. |
B.To describe the recycling program. |
C.To discuss whether or not recycling should be compulsory. |
D.To tell people how to tell different sorts of rubbish cans apart. |
7 . California Preps for Fire Season
WINDSOR, Calif—Grass and other vegetation have begun to cover the ash left behind when the largest blaze of the 2019 wildfire season burned the edge of this Northern California town about four months ago.
“It's not an accident that Windsor got saved,” Mayor Dominic Foppoli said. “We went through 2017. We watched it happen again in Paradise.”
Forecasters expect warmer and drier weather in California heading into spring, which could cause grasses to dry out and lead to an earlier than normal start to this year's fire season.
"We have indicators that we're drying out already," said Scott McLean, a spokesman for the California Department of Forestry and Fire Protection, or Cal Fire.
A.The season used to take off around June but has been starting earlier and earlier for the past few years. |
B.With deadly and destructive wildfires burning every season, California communities are preparing for the worst. |
C.Firefighters in the area were challenged by constantly shifting winds and narrow, winding roadways. |
D.Windsor still stands because most of its residents grabbed pre-packed emergency go-bags and evacuated immediately when ordered |
E.A few days later. Windsor officials stood roadside with signs to welcome residents back. |
F.Many also are reconsidering building codes and emphasizing the need to create defensible spaces by limiting flammables around homes and businesses |
8 . Dandelions
I remember as a young child bringing a bunch of brilliant yellow flowers to my mother. It didn’t matter that the stems felt sticky or that both my parents cursed the presence of these flowers in the lawn. I thought they were beautiful!
And there were so many of them! We spent hours picking the flowers and then popping the blossoms off with a snap of our fingers. But the supply of dandelions (蒲公英) never ran out. My father or brothers would chop off all the heads with the lawnmower (割草机) at least once a week, but that didn't stop these hardy wonders.
And for those flowers that escaped the honor of being hand-delivered to my mother or the sharp blades of the lawnmower, there was another level of existence. The soft roundness of a dandelion gone to seed caused endless laughter of delight as we unconsciously spread this flower across the yard.
As I worked in my garden last week, pulling unwanted weeds out of the space that would become a haven for tomatoes, corn, peas and sunflowers, I again marveled at the flower that some call a weed.
And I thought, if only I had the staying power of a dandelion. If only I could stretch my roots so deep and straight that something tugging on my stem couldn’t separate me completely from the source that feeds me life. If only I could come back to face the world with a bright, sunshiny face after someone has run me over with a lawnmower or worse, purposely attacked me in an attempt to destroy me. If only I could spread love and encouragement as freely and fully as this flower spreads seeds of itself.
The lawns at my parents' home are now beautiful green blankets. The only patches of color come from well-placed, well-controlled flowerbeds. Chemicals have managed to kill what human interference couldn’t. I hope you and I can be different. I hope that we can stretch our roots deep enough that the strongest poison can't reach our souls. I hope that we can overcome the poisons of anger, fear, hate, criticism and competitiveness.
1. The author’s parents probably viewed the dandelions in the lawn as ________.A.supplies of seeds | B.beautiful wonders |
C.unwanted weeds | D.patches of colors |
A.The flowers were meant as a joyful gift to her mother. |
B.The flowers evolved into a stronger species because of frequent mowing. |
C.The flowers were tough enough to spread new lives themselves. |
D.The flowers that some called a weed were difficult to pull out. |
A.The author’s family enjoyed the dandelions as much as she did. |
B.The author purposefully replaced some dandelions with crops. |
C.The dandelions were never successfully removed from the lawn. |
D.The author felt sorry but encouraged by the fate of the dandelions. |
A.share the inspirations she gained from the dandelions |
B.arouse public awareness to pay close attention to the beauty in life |
C.show the importance of planting dandelions |
D.express the shame that only she saw the beauty of the dandelion |
Population Change of European Birds
The breeding bird populations in Europe have seen a great shift over the past three decades, driven by both climate crisis and human interferences, according to one of the world’s largest citizen science projects on biodiversity.
Overall, 35% of birds increased their breeding range. Dr. Iván Ramírez, senior head of conservation at BirdLife Europe and central Asia, said: “Those birds that have been legally protected have been doing better than those which are not protected. This is a really important message within the European Union. We have one of the oldest policies – the Birds Directive – and we can prove that it works.”
In addition, as the climate warms, forests are stretching into northern and agricultural regions. In parts of northern Europe, there has also been tree planting (mainly for wood and paper) and land abandonment (specifically in Mediterranean areas), which benefited many woodland species such as woodpeckers and warblers but caused damage to a number of other species as well. The research shows a total of 25% of birds now occupy a smaller area.
Generally, farmland birds are bigger losers, suffering overall declines in population and reduced distribution because agricultural intensification means there is less food, such as insects and remainder from harvesting. The State of Nature in the EU 2013-2018 assessment showed 80% of key habitats were in poor or bad condition, and intensive farming is a major driver of decline. The UK’s farmland birds have declined by 55% since 1970.
“Predictably, there are winners and losers. We can see how some species have expanded across the continent rapidly and have begun to colonize UK wetlands. In contrast, we can see ranges shrinking as species of northern Europe feel the impact of climate change, and species such as the dotterel are declining in numbers and range in northern Britain,” he said.
10 . Elephants have four distinct personalities that help their herd survive in the African bush, scientists have found.
With their grey skin, mournful eyes and slow heavy pace, you could be forgiven for thinking elephants are uniformly blue creatures. But scientists have now discovered the largest living land animals have personalities to match their size. In a new study of African elephants, researchers have identified four distinct characters that are common in a herd -- the leaders, the gentle giants, the playful rogues and the reliable plodders.
Each of the types has developed to help the giant mammals survive in their harsh environment and is almost unique in the animal kingdom, according to the scientists. Professor Phyllis Lee and her colleague Cynthia Moss studied a herd of elephants in the Amboseli National Park in Kenya known as the EB family - famous for their matriarch Echo before she died in 2009. Using data collected over 38 years of watching this group, the researchers analyzed them for 26 types of behaviors and found four personality features tended to emerge.
The strongest personality to emerge was that of the leader. Unlike other animals, where leadership tends to be won by most dominant and aggressive individual, the elephants instead respected intelligence and problem solving in their leader. Echo, the matriarch and oldest in the group, her daughter Enid, and Ella, the second oldest female, all emerged as leaders.
The playful elephants tended to be younger but were more curious and active. Eudora, a 40-year-old female in the herd, seemed to be the most playful, consistently showing this trait through out her life while playfulness in some of the other elephants declined with age.
Gentle elephants, which included two 27-year-old females Eleanor and Eliot, caressed and rubbed against others more than the others.
Those that were reliable tended to be those that were most consistent at making good decisions, helped to care for infants in the herd and were calm when faced with threats. Echo and her youngest daughter Ebony seemed to be the most reliable. Professor Less said that elephants with these features tended to be the most socially integrated in the group while those who tended to be pushy and less reliable were more likely to split from the herd.
1. The reason why elephants have four distinct personalities is that ________.A.scientists can distinguish them from each other more easily. |
B.the four personalities can help them survived in Africa. |
C.the elephants will be unique in the animals kingdom. |
D.the elephants can avoid being caught by human beings. |
A.the researchers reached their conclusion by analyzing the data. |
B.the research centered on the 26 types of behavior of the matriarch. |
C.the scientists conducted the research by comparing elephants with other animals. |
D.Professor Phyllis Lee and her colleague spent nearly 38 years tracking the herd. |
A.mother and daughter | B.the two oldest female |
C.the most gentle ones | D.leader and member |
A.Not all the types can help the elephants survive in their environment. |
B.Leadership tends to be won by the most dominant and aggressive elephant. |
C.The playful elephants not only tended to by younger but also were more curious. |
D.The reliable elephants are likely to rely on others to decide what to do. |